2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/33670The relation between the technique of conformal flat and Damour-Ruffini-Zhao's method is investigated in this paper. It is pointed out that the two methods give the same results when the metric has the form $g_{αβ=0},$ with $α=0,1$ and $β=2,3$. It is indicated that the two methods are not equivalent for general case.6 pages, LaTeXGeneral Relativity and Quantum Cosmologytext